To be honest, unless you have an AF system like the 7D and you're going to make use of it (i.e. you're a sports/wildlife shooter) the non-Canon performance isn't so bad. It's noticeable but far from a problem. If I was shooting professionally or "must get the shot" then definitely the official Canon lenses are the way to go. The biggest eye opener was how much better the 70-200 f/2.8 II was on ANY body, let alone the 7D2. It's the next lens on my wishlist, absolutely awesome!
On balance, I'd rather have the reach of the 150-600 and suffer from the occasional missed shot if the focus hunts too long. For instance, most of the shots of that kingfisher are blurred not because of AF but because the thing was just so damn fidgety! Same for the yellow bird (black-naped oriole), they are both extremely skittish.
What's interesting is I've been using the 760D too recently and using the same 150-600mm lens I noticed the same odd behaviour on both. Specifically, I'll be focused on a bird and then suddenly for one frame the lens jumps to just past infinity, then back to perfect focus again. It's like it has a minor crisis of confidence and just wants to be sure it's accurate! That said, it's on one-shot focus mode when that happens and not AI servo; I've not had that problem with AI servo. That for me screams dodgy lens AF-implementation.
Personally for me I loved having the AF of the 7D2 at my disposal but it actually made me appreciate my decision to get the 6D - by which I mean at the time I was debating 6D vs 5D3 and the AF was the single biggest niggling point. Now I've used a proper AF system I can see why people like them but the way I shoot I don't miss it day to day. If anything, I'd be inclined to get either a 7D2 for cheaper or perhaps wait for the 5DSR and crop in. We shall see
